Looking at State Route 24 today and in the year 2030 illustrates the need for a fourth bore at the Caldecott Tunnel.

• Bi-directional bottleneck: The Caldecott Tunnel causes bottlenecks for both eastbound and westbound traffic, creating congestion that persists during off-peak periods and weekends. Delays are often unpredictable. The character of these delays is similar to those caused by major freeway incidents or accidents.
• Lane reversals: State Route 24 is reduced from eight lanes to six lanes at the Caldecott Tunnel (three two-lane tunnels). To reduce congestion in the peak direction during the week, the middle bore is reversed between 2:00 a.m. and 5:00 a.m. to favor westbound traffic, and then switched again between 11:30 a.m. and 12:30 p.m. to favor eastbound traffic
• Weekend Traffic: Additionally, weekend traffic is notoriously difficult to predict. Sporting events, concerts and other events make balancing weekend traffic through the tunnel very difficult. It is not uncommon to reverse the middle bore six times on a Saturday or Sunday.
• Future Traffic: The need to add additional lanes by building a fourth bore becomes increasingly evident considering the likelihood of increases in daily delay by the year 2030. Currently, the existing delay is 9,000 hours on a typical weekday and 4,600 hours on a typical Saturday. By the year 2030, the total daily delay is estimated to be 88,000 hours for a typical weekday and 42,000 hours for a typical Saturday.

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